I'm in the process of replacing the engine in my 97 E-350 Chateau 6.8 v10. The a/c system was in need of attention before my engine exploded at 143,000 miles. The a/c system at that time was showing signs of impending compressor failure. Many parts of my a/c system were removed to facilitate engine swap so it is completely evacuated. I'm replacing the compressor, accumulator, both expansion valves and flushing the rest of the components outside of the vehicle.

I have purchased all the replacement part but have questions on the proper sequences of events replacing the PAG 46 into the system. My a/c system calls for 13oz of oil and 64oz coolant and I did not measure any oil that was lost during removal. I have access to a vacuum pump and a/c gauges. I have been searching the internet yet haven't found a site that deals specifically with my circumstances. I'm eager to learn.

 

I'm hoping someone at our Auto Restoration Club has a/c experience while I'm working there.

 

Today I saw an A/C recovery unit in storage at the Auto Restoration shop. I need to get it out and have a closer look. Won't that machine also do vacuum duty before I install my oil and R134A coolant?

 

Typically those recovery units will do every necessary operation relating to evacuating and recharging an A/C system.

Get the brand name and model number to find the operating manual and read up on that----you should be able to do a great job just knowing how to operate that equipment.

 

Where is the proper place to add the 13oz of PAG 46? I know some goes directly into the compressor, but will it hold 13oz.?

 

No, depending on the compressor, they are more like 5 - 7 Oz.
Shop manual usually has a table for suggested amounts/places, depending on what is being replaced. In your case, with replacing major components and flushing, the rest gets parceled out to various components - accumulator, condensor, evap if accessible.

Depending on where your Hi and Lo service ports are physically located, may want to do a bit of thinking about what happens when you evacuate, that you are not putting a lot of oil into something/somewhere that is right by a service port, so the vac pump doesn't slurp out some of your oil as you evacuate. Usually, the big accumulators are safe, as are condensors.
I found that the Hi-side Receiver/Dryer on our Escape (did a pre-emptive replacement of it as it was known to have high failure rate of dessicant bag rupture) was not so safe, some of the oil I put into it ended up in my hoses. Had to use an oil injector to replace what came out.

As I have remarked in other posts on the topic, I always crank out the oil that comes already in the compressor into a measuring cup. Record the amount, throw that oil away. Put that amount of new oil into compressor, turning shaft CW to distribute, but not enough to pump it out. Shop manual will say what the usual proper compressor charge is, so you can see if what you pumped out was correct.

Look at how your compressor mounts, relative to the ports on it. If they point mostly upwards, ok. If they point out sideways or downwards, some of the oil you put in the compressor will drip out as you try to mount it, in that case go lighter on the compressor oil amount, and heavier on the accumulator to balance it out.

Why throw away the oil that comes in the compressor? In an auto assembly plant, they get compressors in that were JIT, so the oil is days/week old. When we buy replacement compressors, they could have been sitting for year(s). PAG oils readily absorb moisture. The shipping plates or plastic shipping plugs on the replacement compressor do not seal as well as the regular system, in my and others opinion. It also allows you to do a sanity check on the amount of oil they actually put in.

 

Thanks for the reply

My compressor shipped dry. Since all of my components are dry and out of the vehicle I will distribute the oil throughout the system, correct?

 

I'll flush all the old components soon, then assemble and vacuum. I tested my new MasterCool gauges the other day and they are still holding vacuum after two days. Ready to use them on my system.

 

I haven't dealt with the dual AC systems in vans, but when putting in a new compressor, accumulator, orifice tube, etc on a normal single system, the directions say to put 1/2 the oil in the compressor suction and half in the accumulator. The once everything is hooked up, but still has no refrigerant, you turn the compressor over by hand several times to move the oil through it so it isn't hydro locked on initial system startup.

 

I installed the new compressor and accumulator today. The compressor holds about 4-5 oz. of PAG46. I will split the rest between the accumulator and the condenser. The screen before the expansion valve on the front evaporator was a mess. It must have been the original as the screen was full of stuff!

I haven't flushed the condenser or rear lines and evaporator yet.

 

I finished the a/c system rebuild yesterday. Flushed all used components and installed new O-rings. Put the PAG 46 in and hooked up the vacuum pump. I let it run for about an hour on Monday. I checked it today and it's still holding the same as when I turned the pump off yesterday, close to 30 hg nearly 24 hrs later. I'm a happy camper!

Do I need to run the vacuum pump more before I charge the system with R134A tomorrow ?

 

I probably would...

If you have not done this before, think about how you are going to get the slug of air out of the yellow charging hose, assuming you have a 3-hose manifold, and not a 4-hose manifold.

With both manifold valves closed to keep system vacuum, attach the can of your choice to the yellow hose. Pierce can/open can valve. Then slightly loosen the yellow hose up at the manifold end, and listen for the hiss, allow air in hose to be pushed out by refrigerant gas, then hand-tighten the hose again. Now, the only air is a little bit in the manifold itself, unavoidable with a three-hose manifold (unless one uses a tee or wye and another hose, splitting the yellow hose into two, one to vac pump, other to can).

Each can that you add, need to re-do the purge procedure. It's simple, but effective.

Also, with the cans, I always use a 1 gallon bucket filled with hot water to hold the can down into while charging. I keep the top of the can above water level, so as not to get water on valve and seating area. The hot water keeps the can pressure up as it empties, because as the liquid refrigerant flashes to gas, it cools the can, which would otherwise drop the pressure. I just lift the can up and shake it once in awhile, and feel how far up the cold area gets. That's the level of refr. remaining in the can at that moment.

 

Started the new v-10 for the first time yesterday. I charged the system and added the required 4 lbs R134A. It worked great at first then after driving for a few miles not so much. I rechecked the pressures again and they were high so I adjusted for the outside temp. Took a short drive and the rear air went hot. I didn't replace the rear expansion valve as it was not that old, my mistake. I'll feel the rear lines today while the a/c is running to see if the rear lines are cold, then punt!

 

I rechecked the pressures this morning and they were low. I adjusted the pressures and took a drive 30 miles to my tranny shop, another issue. Both front and rear systems worked fine!

 

I drove the van today and the rear air quit again. I have ordered a new condenser and rear expansion valve. While I have the rear apart I think I'll check and see if my system has a heater flapper.